In the past, printing units of printing presses have been driven by a main drive which distributes its drive power to the individual units of a printing press via a mechanical line shaft. The printing units are connected and coupled to one another by said mechanical line shaft in such a way that their synchronized running with respect to one another is also possible. In order to realize this, however, a complex mechanical system is necessary with a large number of different components such as gear mechanisms and clutches. The weak points which result from this, such as transmission errors on account of yielding of mechanical transmission members, play, elasticity and additional large inertial masses, impair the printed image, however.
Attempts have been made to eliminate this deficiency by a separate, electromotive drive being assigned to every printing unit or its cylinder. A separate printing drive of this type, which is also called a direct drive, for one cylinder of a printing press is already known from DE 41 38 479 C3. Said drive makes it possible that a drive train which is free of play, low in inertial mass and mechanically rigid can be constructed for every cylinder or every roll of a printing unit. The masses which are to be moved are connected rigidly and fixedly to the rotor of the driving electric motor directly, with the preclusion of elasticity, yielding and play, the associated stator likewise being connected to a stationary wall, for example a printing press wall, in a manner which is free of elasticity and play. As can be gathered from FIG. 7 of this prior publication, a cylinder of a printing unit is provided at one end side with a journal of reduced diameter. At its end which faces the cylinder, said journal is held by a roller bearing. A rotor of an electric motor is pushed onto the journal in a manner which is spaced apart from said roller bearing, the associated stator of said electric motor being held by an adjustment wall of the printing press. A disadvantage of this arrangement is that it requires relatively high expenditure on assembly, because the bearing which holds the journal and the driving electric motor do not form a unit which is ready for installation.
This form of direct drive is also known from EP 1 277 575 A1. As shown by the associated FIGS. 31, 32 and 33 of this prior publication, the journal of a cylinder of a printing press is held in a housing via a bearing point. In turn, this bearing point is adjoined by an electric motor, the rotor of which is pushed onto the journal and the stator of which is accommodated by a housing which is connected to a frame wall. The abovedescribed disadvantages are also apparent here, that is to say the electric motor of the direct drive and the associated bearing of the journal do not form a unit which is ready for installation.